From: Sean Christopherson <sean.j.christopherson@intel.com>
To: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Reto Buerki <reet@codelabs.ch>,
Liran Alon <liran.alon@oracle.com>
Subject: [PATCH v2 1/8] KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter
Date: Fri, 27 Sep 2019 14:45:16 -0700 [thread overview]
Message-ID: <20190927214523.3376-2-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20190927214523.3376-1-sean.j.christopherson@intel.com>
Write the desired L2 CR3 into vmcs02.GUEST_CR3 during nested VM-Enter
instead of deferring the VMWRITE until vmx_set_cr3(). If the VMWRITE
is deferred, then KVM can consume a stale vmcs02.GUEST_CR3 when it
refreshes vmcs12->guest_cr3 during nested_vmx_vmexit() if the emulated
VM-Exit occurs without actually entering L2, e.g. if the nested run
is squashed because nested VM-Enter (from L1) is putting L2 into HLT.
Note, the above scenario can occur regardless of whether L1 is
intercepting HLT, e.g. L1 can intercept HLT and then re-enter L2 with
vmcs.GUEST_ACTIVITY_STATE=HALTED. But practically speaking, a VMM will
likely put a guest into HALTED if and only if it's not intercepting HLT.
In an ideal world where EPT *requires* unrestricted guest (and vice
versa), VMX could handle CR3 similar to how it handles RSP and RIP,
e.g. mark CR3 dirty and conditionally load it at vmx_vcpu_run(). But
the unrestricted guest silliness complicates the dirty tracking logic
to the point that explicitly handling vmcs02.GUEST_CR3 during nested
VM-Enter is a simpler overall implementation.
Cc: stable@vger.kernel.org
Reported-and-tested-by: Reto Buerki <reet@codelabs.ch>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/vmx/nested.c | 10 ++++++++++
arch/x86/kvm/vmx/vmx.c | 10 +++++++---
2 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 41abc62c9a8a..b72a00b53e4a 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2418,6 +2418,16 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
entry_failure_code))
return -EINVAL;
+ /*
+ * Immediately write vmcs02.GUEST_CR3. It will be propagated to vmcs12
+ * on nested VM-Exit, which can occur without actually running L2 and
+ * thus without hitting vmx_set_cr3(), e.g. if L1 is entering L2 with
+ * vmcs12.GUEST_ACTIVITYSTATE=HLT, in which case KVM will intercept the
+ * transition to HLT instead of running L2.
+ */
+ if (enable_ept)
+ vmcs_writel(GUEST_CR3, vmcs12->guest_cr3);
+
/* Late preparation of GUEST_PDPTRs now that EFER and CRs are set. */
if (load_guest_pdptrs_vmcs12 && nested_cpu_has_ept(vmcs12) &&
is_pae_paging(vcpu)) {
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d4575ffb3cec..7679c2a05a50 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2984,6 +2984,7 @@ u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa)
void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
{
struct kvm *kvm = vcpu->kvm;
+ bool update_guest_cr3 = true;
unsigned long guest_cr3;
u64 eptp;
@@ -3000,15 +3001,18 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
}
- if (enable_unrestricted_guest || is_paging(vcpu) ||
- is_guest_mode(vcpu))
+ /* Loading vmcs02.GUEST_CR3 is handled by nested VM-Enter. */
+ if (is_guest_mode(vcpu))
+ update_guest_cr3 = false;
+ else if (enable_unrestricted_guest || is_paging(vcpu))
guest_cr3 = kvm_read_cr3(vcpu);
else
guest_cr3 = to_kvm_vmx(kvm)->ept_identity_map_addr;
ept_load_pdptrs(vcpu);
}
- vmcs_writel(GUEST_CR3, guest_cr3);
+ if (update_guest_cr3)
+ vmcs_writel(GUEST_CR3, guest_cr3);
}
int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
--
2.22.0
next prev parent reply other threads:[~2019-09-27 21:46 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-27 21:45 [PATCH v2 0/8] KVM: x86: nVMX GUEST_CR3 bug fix, and then some Sean Christopherson
2019-09-27 21:45 ` Sean Christopherson [this message]
2019-09-27 23:37 ` [PATCH v2 1/8] KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter Jim Mattson
2019-09-27 21:45 ` [PATCH v2 2/8] KVM: VMX: Skip GUEST_CR3 VMREAD+VMWRITE if the VMCS is up-to-date Sean Christopherson
2019-09-27 21:45 ` [PATCH v2 3/8] KVM: VMX: Consolidate to_vmx() usage in RFLAGS accessors Sean Christopherson
2019-09-30 8:48 ` Vitaly Kuznetsov
2019-09-27 21:45 ` [PATCH v2 4/8] KVM: VMX: Optimize vmx_set_rflags() for unrestricted guest Sean Christopherson
2019-09-30 8:57 ` Vitaly Kuznetsov
2019-09-30 15:19 ` Sean Christopherson
2019-09-30 15:55 ` Vitaly Kuznetsov
2019-10-09 10:40 ` Paolo Bonzini
2019-10-09 16:38 ` Sean Christopherson
2019-10-09 20:59 ` Paolo Bonzini
2019-10-09 21:30 ` Sean Christopherson
2019-09-27 21:45 ` [PATCH v2 5/8] KVM: x86: Add WARNs to detect out-of-bounds register indices Sean Christopherson
2019-09-30 9:19 ` Vitaly Kuznetsov
2019-10-09 10:50 ` Paolo Bonzini
2019-10-09 16:36 ` Sean Christopherson
2019-09-27 21:45 ` [PATCH v2 6/8] KVM: x86: Fold 'enum kvm_ex_reg' definitions into 'enum kvm_reg' Sean Christopherson
2019-09-30 9:25 ` Vitaly Kuznetsov
2019-10-09 10:52 ` Paolo Bonzini
2019-10-09 11:27 ` Vitaly Kuznetsov
2019-09-27 21:45 ` [PATCH v2 7/8] KVM: x86: Add helpers to test/mark reg availability and dirtiness Sean Christopherson
2019-09-30 9:32 ` Vitaly Kuznetsov
2019-10-09 11:00 ` Paolo Bonzini
2019-09-27 21:45 ` [PATCH v2 8/8] KVM: x86: Fold decache_cr3() into cache_reg() Sean Christopherson
2019-09-30 10:58 ` Vitaly Kuznetsov
2019-09-30 15:04 ` Sean Christopherson
2019-09-30 15:27 ` Vitaly Kuznetsov
2019-09-30 15:33 ` Sean Christopherson
2019-10-09 11:03 ` Paolo Bonzini
2019-09-30 10:42 ` [PATCH v2 0/8] KVM: x86: nVMX GUEST_CR3 bug fix, and then some Reto Buerki
2019-10-29 15:03 ` Martin Lucina
2019-10-30 9:09 ` Sean Christopherson
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